Protein texturization by centrifugal spinning

ABSTRACT

A bland texturized monofilament protein product having a texture and mouth feel simulating animal meat is prepared by forming an aqueous slurry of a protein material, injecting high pressure steam into the slurry to propel it through a confined treatment zone, centrifugally spinning the protein material into monofilaments, and recovering the textured monofilaments in a collection zone. Apparatus for performing this process comprises means for injecting steam into a protein slurry, means defining a confined treatment zone wherein the injected steam and protein are contacted, and means for centrifugally spinning the steam-treated protein material into monofilaments.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to the treatment of untextured protein materialsto form a product possessing the fibrous texture and mouth feelproperties of animal meat.

2. Description of the Prior Art

The food industry has spent much effort over a span of many years andhas expended large sums of money in an attempt to utilize non-meatproteins, such as those derived from vegetables, as additives to orsubstitutes for animal meat products. It long has been recognized thatthe ever-increasing worldwide food shortage could be in material partobviated if only such relatively inexpensive materials could beconverted into products so closely approximating the naturally occurringfood material that public acceptance would be achieved. One of the majorroadblocks encountered by the industry has been the inability to impartthe natural and accustomed chewy, fibrous texture to vegetable proteinmaterials. Animal meat products inherently possess a texture giving thema definite "mouth feel" which is clearly recognized and stronglypreferred. Vegetable proteins in their natural state generally take theform of amorphous powders which, despite their unquestioned nutritivevalue, possess mouth feel characteristics wholly unacceptable to theconsumer as a meat substitute. Moreover, vegetable proteins normally arecharacterized by objectionable "beany" flavors which the industry hasbeen unable to remove or mask.

In recent years a number of processes and apparatus have been developedfor treating vegetable protein material to produce a bland texturizedproduct. None of these processes, however, has achieved any substantivemeasure of commercial success.

The first generation of these prior art techniques involved the wetspinning process disclosed in Boyer, U.S. Pat. No. 2,730,447. Thisprocess produces a fibrous product by extruding a plurality of finestreams of an aqueous solution of protein into a chemical coagulatingbath. The protein coagulates into fine fibers which are collectedtogether and treated to form an edible textured protein product. The wetspinning process suffers from a number of drawbacks in addition to itsgeneral failure to produce an adequately textured product as discussedabove. The equipment employed to perform this process is extremelysophisticated for the food industry and represents a very high initialcost problem. Adding further to the economic infeasibility of theproduct produced by the wet spinning process is the expensive startingmaterials which must be employed. Moreover, product uniformity isdifficult to achieve due to the general complexity of the process andthe numerous parameter control problems presented.

The second generation technique advanced in this area is the extrusioncooking process disclosed in Atkinson, U.S. Pat. No. 3,488,770, in whicha protein mass is physically worked at an elevated temperature andthereafter extruded at an elevated temperature and pressure through anorifice into a medium of lower pressure and temperature. This processalso suffers from high equipment costs. In addition, the productproduced by extrusion cooking has a very low density which swells up inwater to give a "spongy" texture. Moreover, the product containsobjectionable flavor notes in addition to the "beany" flavor originallypresent in the starting materials which are apparently imparted to theproduct by the processing steps.

The third generation of development in the protein texturizationinvolves the use of steam as the texturizing medium. Exemplary of thisapproach are Strommer, U.S. Pat. Nos. 3,754,926 and 3,863,019 whichtreat either finely divided protein particles or slurries with steam andHeusdens U.S. Pat. No. Re. 28,091 which employs a steam treatment of aprotein slurry following complex hydration steps. Products produced bythese processes also possess the general problems of poor texture andflavor discussed above. In addition, the product has low densityproblems similar to the second generation extrusion cooked products inthat on hydration they tend to be very soft. The product is alsoextremely friable.

Other attempted solutions by the art include the cooking and shaping ofa protein dough disclosed in McAnelly, U.S. Pat. No. 3,142,571, and theheat coagulation of undenatured protein disclosed in Rusoff, U.S. Pat.No. Re. 27,790.

Notwithstanding the veritable plethora of prior art attempts tosatisfactorily texturize vegetable proteins--no one to data has made anyreally substantial progress toward the desired goal. The present absencefrom the market of any commercially accepted consumer products based onvegetable protein demonstrates clearly that the problems involved simplyhave not been solved. Indeed, those meat analog products which havefound their way to the supermarket shelves generally have been met withlittle or no consumer acceptance and have generally been withdrawn.Especially in the United States, where consumer preferences rather thannutritional values often dictate the fate of food products, a successfultexturized vegetable protein material simply must possess taste andmouth feel characteristics similar to natural meat. In addition, theprior art processes generally have employed such complex apparatus andprocedures that initial equipment and operating costs have made proteinanalog products economically unattractive to manufacturers, despite therelatively inexpensive nature of the raw product.

Given the ever-increasing fears of worldwide famine and the diminishingavailability of animal meat protein products, it is clear that aninexpensive, consumer-acceptable, high protein food product based ontexturized proteins is urgently needed.

BRIEF SUMMARY OF THE INVENTION

It is the object of the present invention to provide a process andapparatus for texturizing protein which fulfills the need left by theprior art texturizing processes.

More specifically, it is an object of the present invention to provide aprocess and apparatus for producing monofilamentary protein materialhaving a fibrous texture simulating that of natural meat.

It is a further object of the present invention to provide a process andapparatus which will produce a bland flavored protein product.

Another object of the present invention is to provide a process andapparatus which will produce a retort stable protein product.

It is also an object of this invention to provide a texturizing processand apparatus which will produce such a product at a much lower cost dueto lower initial equipment costs and lower operating costs.

Accordingly, the method of the present invention comprises treating aslurry of protein material with an injected stream of heated gas in aconfined zone at elevated temperature and pressure, centrifugallyspinning the treated protein material to form protein monofilaments, andrecovering the texturized protein monofilaments in a collection zone.

The present invention further provides apparatus for producingtexturized protein monofilaments which comprises means for treating aprotein slurry with injected gas at an elevated temperature andpressure, means for centrifugally spinning the protein material intomonofilaments, and means for recovering texturized protein monofilamentsin a collection zone.

BRIEF SUMMARY OF THE DRAWINGS

FIG. 1 is a schematic of the protein texturizing apparatus of thepresent invention.

FIG. 2 shows the construction of one embodiment of the spinnerette heademployed in the present invention.

FIG. 3 is a photomicrograph taken at 25X of a single texturized proteinfiber produced by the process of the present invention.

FIG. 4 is a series of photomicrographs showing the internal structure ofthe fiber of FIG. 3; 4a is taken at 50X; 4b at 100X; 4c at 300X; 4d at500X; 4e at 1000X; and 4f at 1500X.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to a process and apparatus forproducing texturized protein monofilaments. The term texturizing as usedherein and widely understood in the art refers to the process ofchanging globular amorphous particles of protein into fibrous continuousphase protein material having structural integrity.

The term retort stable as used herein refers to a product which keepsits structural integrity after treatment at elevated temperature andpressure. In the typical retort processing test about 1 part texturizedprotein is mixed with 10 parts of a 1% salt solution and sealed in acan. The can then is placed in a retort and subjected to a temperatureof 250° F. and a pressure of 15 psig for about 60 minutes. The abilityof a retorted product to maintain its structural integrity and bitecharacteristics can be tested by placing the product between the thumband forefinger and subjecting the product to shear forces. A retortstable product will not disintegrate with moderate finger pressure. Aproduct with poor retort stability will feel mushy and will fall apartwhen subjected to moderate shear forces.

Protein material employed in the process of the present invention shouldcontain at least 70% protein on a dry weight basis, with 70 to 75%preferred for meat-simulating bite and 90% or higher for a very firm,tough bite. Of primary interest are vegetable protein materials derivedfrom soybean. Soy proteins can take the form of soy flour, soyconcentrate, soy isolates or mixtures thereof. Suitable protein mixturescan consist of from about 50 to 60% soy flour and from about 40 to 50%soy isolate. Other oilseed materials such as peanut, cottonseed andsesame seed may also be employed. Other known protein sources such asthose derived from wheat, milk, eggs, single cell or leaf proteins andthe like may be texturized according to the process of the presentinvention. Protein material employed should be viable, i.e., have a PDI(Protein Dispersability Index) in the range of from 50 to about 90%.

The process and apparatus of the present invention may also be employedto texturize a mixture of meat and a protein binder. Meat proteins maycomprise meat scraps or pieces possessing poor textural qualities suchas mechanically deboned chicken, beef, seafood, and the like or desiredblends. Suitable protein binders include vegetable proteins such as soyprotein or other known proteins such as those derived from wheat, singlecell, leaf, milk, egg, and the like. In general, mixtures containing upto about 80% comminuted meat may be texturized according to the processof the present invention. For most applications, mixtures containingfrom about 50 to about 75% meat provide the best results.

In accordance with the process of the present invention the proteinmaterial described above initially is mixed with water to form adough-like proteinaceous slurry. This slurry should contain about 40 to50% solids. If desired, a pumping aid such as, for example, sodiumbisulfite, may be employed to reduce the viscosity of the slurry. Theprotein slurry then is treated with steam in a confined zone maintainedat an elevated temperature and pressure. Preferably, this steamtreatment takes place in a jet-cooking apparatus. In this type ofapparatus, the slurry is advanced through a feed pipe to a steaminjection zone by a feed pump. The slurry feed rate will depend on theparticular apparatus employed. In pilot plant size apparatus, rates ofabout 6 to 15 pounds per minute have been employed, whereas inproduction applications, rates of from about 20 to 50 pounds per minuteor more may be employed. High pressure steam then is injected directlyinto the protein slurry in the injection zone. The high steam pressureand the resulting turbulence insures rapid and uniform heat transfer tothe protein slurry. The steam pressure should be sufficiently high toovercome the pressure of the slurry from the feed pump and to propel theslurry out of the steam injection zone. Pressures in the range of about80 to about 150 psi are suitable to achieve this result. Best resultsare achieved when the steam pressure is in the range of about 100 toabout 120 psi.

The high pressure steam flow leaving the injection zone propels theprotein slurry into a confined treating zone. A predetermined elevatedtemperature and pressure are maintained in the confined treating zone torender the protein into a thermoplastic state. The protein productshould be held under pressure in the confined treating zone until atemperature of about 310° to 350° F. is reached. Preferably,temperatures of about 325° to about 350° F. are employed. The residencetime in the confined zone is not critical and may range from a fewseconds up to one or two minutes. Residence time values may becontrolled by varying the slurry feed rate and the length of the zone.

The protein material which has been rendered thermoplastic by thepreceding steam treatment next enters a rotating multi-orificespinnerette head located at the discharge end of the confined treatingzone. The centrifugal forces created along the axis of the spinneretteact to draw, stretch, and orient the emerging protein monofilaments.Spinnerette rotations in the range of about 1000 to about 2000 RPM aresuitable to form monofilaments. Optimum results are achieved at about1800 RPM. By varying the spinnerette RPM's and the pressure andtemperature conditions in the cooking tube, fiber lengths from about 1/2to about 6 inches can be obtained. The spinnerette head further servesto maintain a back pressure of about 70 to 80 psi in the confined zone.

In the preferred embodiment the fibers emerging from the spinnerette arequenched by sprays of a cooling fluid, e.g., water, directed at theproduct. The resulting stream of water is useful to carry the productout of the centrifuge and into a collection zone where the fibers arerecovered in a known manner.

In another embodiment of the present invention the centrifuge may beoperated without the water sprays. In this embodiment the filamentaryproduct is allowed to build up on the walls of the recovery zone to forma belt-like structure of fused filaments all oriented in the directionof rotation. This belt or shell of fused product may be cutlongitudinally and removed from the recovery zone as a unitary piece.When this large piece is diced, it exhibits a fused fiber bundlestructure which closely resembles muscle fiber.

In a further embodiment the thermoplastic protein material in thecooking tube is subjected to stretching forces before it reaches thespinnerette head. This stretching step is preferably accomplished bypassing the thermoplastic protein material through an orificerestriction, i.e., a washer-like obstruction in the flow path whicheffects a momentary reduction of the cross section in the cooking tube.By way of example, a restriction means having an orifice diameter offrom about 7/16 to 13/16 inch have been successfully utilized in a 11/2inch cooking tube. The internal structural characteristics of the spunprotein fibers are enhanced by this additional treatment.

One embodiment of the apparatus of the present invention now will bedescribed by reference to FIG. 1. The slurry of protein to be texturizedand water is formed in any suitable mixing means 1 such as a Hobartmixing bowl. Discharge from the mixing means is forwarded by a feedingmeans 2 communicating through a feed line 3 with a steam injection zone4. The feeding means can be any device capable of forwarding arelatively high consistency slurry. Positive displacement pumps such asthe "Moyno" pump are well suited for this application. The feed line cancontain a pressure gauge 5 and a check valve 6 which is effective toprevent back flow in the feed line.

Steam injection zone 4 comprises a mixing valve assembly in which theprotein slurry from the feed line and high pressure steam are mixed. Anyvalve assembly which can effect a rapid and intimate mixture of steamand protein slurry without clogging can be employed. One suitable valveis the Schutte & Koerting Model #320 11/4" NPT. Steam enters theinjection zone via inlet line 7. Communicating with the discharge fromthe injection zone is a confined treating zone 8. In the preferredembodiment this treating zone comprises an elongated cylindrical chamberor cooking tube. The dimensions of this chamber are not critical. Inpractice, lengths of from 7 to 13 feet have been satisfactorilyemployed. The diameter should be large enough to prevent clogging andsmall enough to facilitate the maintenance of proper pressureconditions. Diameters in the range of about 11/2 to 6 inches have beenfound to satisfy these conditions although a maximum of 3 inches ispreferred. The chamber may be provided with temperature sensing element9, and a discharge pressure gauge 10.

The discharge end of the cooking tube is provided with means forcentrifugally spinning the protein material, generally shown as 12. Thecentrifugal spinning means comprises a rotating multi-orificespinnerette head 13 which is driven by a motor 14 or other suitablemeans. Cold water spray nozzles 15 may also be provided to quench theemerging monofilaments. The cold water nozzles are preferably arrangedconcentrically outside and above the spinnerette head. The centrifugeassembly is also provided with a product recovering zone 16 in which themonofilaments and water mixture may be collected. The cross section spunfibers may be varied by employing spinnerette orifices of differentshape.

Details of the preferred spinnerette head assembly are shown in FIG. 2.Rotary joint 21 receives the protein material from the cooking tube andfeeds it to the spinnerette head 22. Spinnerette orifices 23 provideoutlets for the spun product. The entire assembly is rotated by acentrifuge motor (not shown) through drive shaft 24 coupling 25.

The product produced by employing the process parameters and apparatusof the present invention is a monofilamentary texturized proteinmaterial having structural and eating properties similar to animal meatproducts. The product possesses good striated muscle laminate structurewhich heretofore could not be achieved by the prior art. As shown inFIG. 3, this product also possesses a very dense complex matrix andexcellent random cross fiber development. This structure exhibitsexcellent mouth feel, i.e., the bite and shear properties of the productof the present invention simulate the chewing of animal meat tissue.Furthermore, the product is free from objectionable flavor notes whichoften made prior art products unacceptable to humans. Another advantageachieved by the process and apparatus of the present invention lies inthe retort stability of the product. Thus, the protein product may beprocessed by conventional food preparation techniques without thermaldegradation of its physical properties.

Products produced by the process of the present invention find utilityin a number of food processing fields. The fibrous textured proteinmonofilaments may be combined with suitable binders and adjuvants toprovide meat analogs having the appearance, taste, and chewability ofanimal meat products. These fibers have particular utility in theformation of seafood analogs such as lump crabmeat or lobster meat. Thetexturized protein product produced according to the embodiment of thepresent invention using no water sprays may be diced or otherwise cutinto portions suitable for direct incorporation into canned or frozenfoods. The texturized protein product of the present invention may alsobe employed as a filler or extender in ground meat products. It is alsopossible to produce fabricated nutrients from the protein materialproduced according to the present invention.

The process of the present invention is also useful to upgrade orrestructure meat scraps or by-products with little or no food value dueto their poor structural characteristics.

The following specific examples are intended to illustrate more fullythe nature of the present invention without acting as a limitation onits scope.

EXAMPLE 1

Textured soy protein monofilaments are produced according to the processof the present invention as follows: 4,282 grams of protein mixturecomprising 50% Promine R (a soy isolate containing about 95% proteinproduced by Central Soya, Inc.) and 50% Soy Flour 200W (a soy flourcontaining about 50% protein produced by Central Soya, Inc.) is slurriedwith water to provide a solids content of 40%. 20 grams of sodiumbisulfite is added to the slurry to decrease its viscosity. This slurryis texturized in the apparatus of the present invention as shown inFIG. 1. The slurry is formed in a Hobart bowl mixer equipped with pastryhooks and forwarded by a Model 3L4 Moyno pump. The steam mixing valve isa Schutte & Koerting Model #320 11/4" NPT. The steam supply is 110 psiand in this apparatus the resulting steam velocity is in the range ofabout 50' per second. The temperature in a 11/2" diameter, 10' longcooking tube is maintained at 320° F. The back pressure in the cookingtube is about 70 psi. The orifices in the spinnerette head are set at0.070" and the head is rotated at 1800 RPM. The product issuing from thespinnerette head consists of 2 to 3" fibers which are quenched by awater spray. The fibers are very white and exhibit good texturalqualities.

EXAMPLE 2

This example demonstrates another embodiment of the present inventionwhich comprises allowing the spun fibers to build up and fuse on thesides of the recovery zone. Textured protein fibers are spun as inExample 1, but this time the water sprays are not employed. The fibersare allowed to build up and fuse on the inside wall of the recovery zoneand then are removed. The resulting belt-like protein mass is quenchedwith cold water at 50° F. and diced. Upon retort processing the dicedprotein material exhibits good color and stability. The texture of thismaterial consists of a unidirectional bundle of fused spun fibersclosely resembling muscle fibers.

EXAMPLE 3

In this example the protein material consists of 45% Promine R and 55%Soy Flour 200W. The slurry is adjusted to 40% solids and texturized asin Example 1 except that an orifice restrictor having 9/16 inch orificediameter is placed in the cooking tube just upstream from the entranceto the spinnerette head. The back pressure in the cooking tube is 72psi, the spinnerette orifice is set at 0.050", and the head is rotatingat 1800 RPM. The water spray is used for this run. The spun productconsists of thin uniform fibers of approximately 3/4 inch. This productis highly suitable for use in seafood analogs such as crab or lobstermeat.

While certain specific embodiments of the invention have been describedwith particularity herein, it should be recognized that variousmodifications thereof will occur to those skilled in the art. Therefore,the scope of the invention is to be limited solely by the scope of theclaims appended hereto.

I claim:
 1. Apparatus for producing texturized monofilaments of proteinmaterial comprising:(a) means for treating a protein slurry withinjected gas at an elevated temperature and pressure; (b) means forcentrifugally spinning said protein material into monofilaments; and (c)means for recovering texturized protein monofilaments in a collectionzone.
 2. The apparatus of claim 1 wherein said means for treatingcomprises an elongated confined zone through which said protein slurryis propelled by a flow of said injected gas.
 3. The apparatus of claim 1wherein said means for centrifugally spinning comprises a rotatingmulti-orifice spinnerette head.
 4. The apparatus of claim 3 wherein saidmeans for centrifugally spinning additionally comprises means fordirecting a spray of cooling fluid on the protein monofilaments issuingfrom said spinnerette head.
 5. Apparatus for producing texturizationmonofilaments of protein material comprising:(a) means for mixing asource of protein and water to form a slurry; (b) means for advancingsaid slurry to an injection zone; (c) means for injecting a gas flowinto said slurry in said injection zone; (d) means defining a confinedtreating zone communicating with said injection zone, whereby said gasflow propels said slurry into and through said confined treating zone;(e) means for centrifugally spinning said protein material intomonofilaments; and (f) means for recovering texturized proteinmonofilaments in a collection zone.
 6. The apparatus of claim 5 whereinsaid means for centrifugally spinning comprises a rotating multi-orificespinnerette head.
 7. The apparatus of claim 6 wherein said means forcentrifugally spinning additionally comprises means for directing aspray of cooling fluid in the protein monofilaments issuing from saidspinnerette head.